This invention relates to novel ultraviolet-emitting phosphors and to methods of preparation thereof.
Very little is known about inorganic cathodoluminescent materials which can emit at wavelengths below 3000 A, and very few such phosphors are known. One such phosphor, disclosed in U.S. Pat. No. 2,770,749 to A, Bril et al., is a self-activated zirconium pyrophosphate phosphor (ZrP.sub.2 O.sub.7). This phosphor contains highly-charged zirconium ions with an np.sup.6 nd.sup.0 configuration. The emission is believed to come from the metal ions themselves, through charge transfer transitions between the O.sup.2.sup.- anions and the central metal ion. No activators are needed for this process.
The novel phosphors herein consist essentially of hafnium pyrophosphate wherein 0 to 20 mole percent of the hafnium is substituted with at least one of zirconium, germanium and silicon. The unsubstituted species may be represented by the molecular formula HfP.sub.2 O.sub.7. The phosphors are prepared by heating in air at temperatures of about 1000.degree. to 1300.degree. C mixtures of a hafnium compound and a phosphate for a period of at least 30 minutes. No additional ions are required to activate the phosphor.
The novel phosphors are roentgenoluminescent, cathodoluminescent and photoluminescent, emitting in broad spectral bands which peak at about 2600 to 3000 A. The novel phosphors may be used for their ultraviolet emission; for example, in cathode-ray display tubes, flying spot scanners, or in any of the applications mentioned in the above-cited patent to Bril et al.